Hearing-impaired individuals may benefit from communication systems and devices configured to provide assistance in order to communicate with other individuals over a communication network. For example, relay services have been established to provide assistive services (e.g., text captions) to the hearing-impaired user communicating with a communication device (e.g., caption phone, caption enabled device, etc.) that is specifically configured to communicate with the relay service.
In particular, a relay service may be a telecommunication intermediary service, which is intended to permit a deaf or a hearing-impaired person to utilize a normal telephone network. The relay service may include an operator, referred to as a “call assistant,” who serves as a human intermediary between the hearing-impaired user and a far-end user. During a captioning communication session, the call assistant may listen to the audio signal of a far-end user and “revoice” the words of the far-end user to a speech recognition computer program tuned to the voice of the call assistant. Text captions (also referred to as “captions”) may be generated by the speech recognition computer as a transcription of the audio signal of the far-end user, and then transmitted to the communication device being used by the hearing-impaired user. The communication device may then display the text captions while the hearing-impaired user carries on a normal conversation with the far-end user. The text captions may allow the hearing-impaired user to supplement the voice received from the far-end and confirm his or her understanding of the words spoken by the far-end user.
During a communication session, the microphone of the communication device may experience echo (e.g., line echo, hybrid echo, acoustic echo). If the audio signal captured by the microphone and transmitted to the far-end user includes acoustic energy produced by the speaker, the far-end user may hear an “echo” of his or her own utterances. Conventional acoustic echo cancellation (AEC) techniques are designed to predict and remove the echo from an electrical signal generated by the microphone. In a communication device configured to assist hearing-impaired users, the issue of echo can present unique challenges due to the much louder volume levels for the audio produced by the speaker for the hearing-impaired user.